When a hormone such as insulin binds to its cell surface tyrosine kinase receptor, a cellular kinase cascade occurs which leads to the activation of phosphatidylinositol-3-kinase. PKB alpha is a pleiotrophic protein that is involved in a large number of different cellular responses to phosphatidylinositol-3-kinase activation. Coffer et al., 1998, Biochem. J. 335:1–13. These responses include increased expression of FAS ligand and antiapoptotic genes, increased cAMP concentration, increased protein synthesis, and increased glycogen synthesis. VanHaesebroack and Alessi, 2000, Biochem. J. 346:561.
Recently, it has been discovered that over-expression of a PKB alpha gene product in mammalian cell lines grown in tissue culture results in cells that have enhanced properties. For example, such cells were better able to grow and produce recombinant proteins in serum-free, protein-free, and/or peptone-free culture medium. PCT/US00/23483.
As more genes are being identified through genomic techniques, the need to rapidly express recombinant proteins for functional studies has become increasingly acute. In addition, as more protein-based drugs demonstrate clinical effectiveness, the need for increased quantities of such proteins for commercial use increases. At the same time, the building and regulatory approval of culture facilities to address this commercial need takes significant investments in both capital and time. Hence, there is a growing need in the art for the optimization of yields of recombinant protein from cultured cells.